The demand for wireless mobile data is increasing. To meet this increasing demand, standards have been developed to increase the spectral efficiency, for example, through the use of better multiple access, modulation and coding, and multi-antenna techniques.
One method considered for capacity improvement is device-to-device direct communication. If wireless transmit/receive units (WTRUs) (e.g., a mobile device or a user equipment (UE)) communicate directly with each other, an alternate topology that co-exists with the conventional cellular deployment may be created. An example application enabled by such direct peer-to-peer communications includes WTRU relaying. In the WTRU relay application, a terminal WTRU (TWTRU) exchanges data with the network through a helper WTRU (HWTRU).
For mobile relay operations and peer-to-peer direct communications WTRUs may need to know their surrounding in terms of the physical presence and movement of their peer WTRUs. This awareness may enable a WTRU to recognize each of its neighbors with further information such as identity, mutual distance, etc.
In current cellular wireless communication systems, a WTRU communicates solely with the infrastructure node (e.g., a base station or a relay) that it is associated with and may not have any knowledge about the surrounding devices.